The GPS, or other GNSS, can be used to determine the position of a user on or near the earth from signals received from multiple orbiting satellites. The latitude, longitude, and altitude of any point close to the earth can be calculated from the times of propagation of the electromagnetic signals from four or more satellites to the unknown location of a GPS or GNSS receiver. In the GPS satellite constellation, each satellite transmits two spread-spectrum signals in the L-band, known as L1 and L2. The L1 signal is transmitted at a center frequency of 1575.42 MHz, while the L2 signal is transmitted at a center frequency of 1227.6 MHz.
Typically, in the GPS, active antenna electronics adjust the gain and the phase of a multi-element antenna array in order to steer the antenna pattern away from an interference source which may serve to jam the satellite ranging signals. In order to adjust the gain and phase, power detection circuitry is used to detect the power in the L1 and L2 bands. With the power detection circuitry, the in-band power can be reduced by changing the gain and phase of the multi-element antenna array. If the GPS receiver is adapted to utilize only one of the L1 and L2 frequency band signals, it would be necessary to detect the power in only that corresponding one of the L1 and L2 frequency bands. However, if the GPS receiver utilizes both of the L1 and L2 frequency band signals in generating a navigation solution, it is desirable to detect and reduce the power in both bands simultaneously.
The number of components necessary to perform power detection in both the L1 frequency band and the L2 frequency band is significantly greater than the number of components typically needed to detect power in only one of these two frequency bands. In the prior art, two separate RF paths are used in the power detection circuitry, one to detect L1 frequency band signals and one to detect L2 frequency band signals. In addition to requiring two separate RF paths and significantly more circuitry, switching between power detection only in the L1 frequency band, power detection only in the L2 frequency band, and power detection in both the L1 and L2 bands simultaneously potentially adds a great deal of complexity to the circuitry.